Core C provides molecular assays for identifying, tracking, and quantifying cellular clones within complex multi-clonal mixtures. This function is designed to support basic stem cell biology, stem cell transplantation, and gene therapy research within the CCEH research base, but also among a broader community of basic and clinical scientists, at the FHCRC, UW, and other institutions. Services provided include VNTR analysis (Variable Number Tandem Repeat), to track the level of donor contribution in a transplant setting and LAM-PCR (Linear Amplification-Mediated PCR) to identify and track specific clones of cells in a chimeric mixture. Techniques are in place to estimate the level of gene transfer into stem cells, to estimate the number of stem cells engrafting, to detect the recruitment and exhaustion of individual stem cell clones, to identify leukemic outgrowth, and to determine insertion site specificity of retroviral vectors. A third assay category. Allele Tracking, has been added more recently to assist in the validation of transgenic and knockout mice developed by our users. To this end, we have developed nine multiplex PCR assays to quickly track the genotypes of several conditional knockout lines. Additional assays are developed a needed.